The safe operation of reactors, boilers and other pressure vessels requires the regular inspection of the vessel and its interior parts. In the case of pressure vessels with tube bundles, each tube must be examined for scaling, cracks or ruptures. For certain types of vessels such as ethylene oxide reactors, the tube bundles are oriented vertically. Thus, the inspection requires an individual in the lower head to shine a light through each individual tub while a second individual looks down that same tube to identify any defects or plugging. If defects are located, the tube can be blocked off at the top and bottom ends or marked for cleaning or other treatment. Once cleaned, the tube must be reinspected.
These tube bundles are typically forty feet long or longer and contain thousands of tubes. The inspection service, even without cleaning and reinspection, is extremely time consuming. Plus, small cracks at the far end of the tube can be difficult to see. This is further complicated by identifying and locating tubes to be cleaned and reinspected.
Taking one of these vessels out of service can cost hundreds of thousands, and in some cases, millions of dollars a day. This provides a huge incentive to work as quickly as possible. This time pressure can lead to further inaccuracies in the work.
What is needed is a way to speed up and increase the accuracy of these inspections.